Among numerous machines, including paving machines, front wheel loaders, excavators, road graders, milling machines, and construction machines, the demand for more sophisticated engine controls is ever increasing.
During roadbed paving operations, and particularly at times of reduced workloads, less than full engine power may be required for effective performance of a paving machine being utilized, as one example. Such periods of reduced workload present opportunities for increasing fuel efficiency as well as for reducing machine noise. Many conventional machines supplement a so-called normal power idle mode with an economy idle mode for such purpose. The economy mode offers a relatively low engine idle speed during periods of reduced workload demand, while permitting an operator to switch back to normal power (higher) engine idle speed whenever the machine may encounter higher workloads. Although the normal power engine idle mode generally produces a relatively high idle speed irrespective of workload, the normal mode has an advantage of being more immediately responsive to abrupt changes in workload demand. For example, under the normal power mode, there is less risk of the engine becoming bogged down upon encounters of transient and/or spontaneous increases in workload demand.
Several efforts have been made to enhance engine control responsiveness as a function of anticipated loads. However, most of these efforts have resulted in relatively complex and expensive systems. For example, U.S. Pat. No. 7,353,105 discloses an engine control device for construction machinery that involves controlling engine idle speeds between a normal power mode and an energy-saving mode. However, that particular control device relies on inputs that include actual vehicle speeds, and incorporates an onboard controller for sending command signals to an electronic control module based on sensed values of the vehicle speed. Responsively to such inputs, the device switches engine idle speeds between those of normal power and energy-saving modes.
Accordingly, it may be beneficial to provide a simpler engine speed control system; albeit one more directly tied to engine workload demand, as opposed to machine speed and other external and/or indirect variables.